FOCUS ON EARTH SCIENCE (4)

48 Chapter 1 Science Content Standards 7.f Read a topographic map and a geologic map for evidence provided on the maps and construct and interpret a simple scale map... Different

The Unique Planet Earth

The structure of our planet, both

inside and out, makes it the only

place in our solar system that harbors

30 Million Years Ago

North American Plate first touches the Pacific Plate, eventually causes the San Andreas Fault.

10 Million Years Ago

San Andreas Fault first moves.

1562

Diego Gutierrez makes first map of Baja California.

c 150

Claudius Ptolemy writes book on geography that includes color maps based

on knowledge of Earth’s surface at the time.

1746

Jean Etienne Guettard presents first map of min- erals in France to French Academy

as the capital of California in 1854.

1912

Alfred Wegener sizes that continents were joined sometime in the past and have spread apart from tectonic plate movement.

hypothe-February 2000

NASA maps show Earth’s entire surface using radar technology

by satellite.

these events and others, visit

43

1932

The first time the Olympics are held in Los Angeles.

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Mapping Earth’s Surface

44

Do you wish to live close to the beach? A single centimeter on this satellite

image of the San Francisco Bay area might represent a long distance on land

Can you tell from this image how steep or flat the ground is? If you look

more closely, you can see the San Andreas Fault Where would it be safe to

build your home?

-Vˆi˜ViÊÊ+PVSOBM

-Vˆi˜ViÊÊ+PVSOBM List some kinds of information you might get from maps

if you were planning to build a new home.

Where would you build your home?

Earth’s surface can be

represented in many ways

Maps provide

>ˆ˜Ê`i> Maps

repre-sent large areas of Earth

at a size we can easily

see and study

maps are used to show

specific features such as

changes in elevation and

geologic characteristics

7.b, 7.c, 7.f, 7.h 7.f

Visit to:

▶ view

▶ explore Virtual Labs

▶ access content-related Web links

▶ take the Standards Check

Start-Up Activities

45

How might you map

your neighborhood?

What would your

neighborhood look like

from the air? How would

you draw it on paper?

Think About This

you see on the ground if you flew in a

plane over your neighborhood?

are in relation to other objects

Procedure

1 Make an empty two-column table In the

left column, list ten objects you would

include in a map of your neighborhood

2 In the right column, draw each object as it

might appear from above

3 Make a list of six symbols to represent

objects such as trees, houses, and roads

4 Draw a map of your neighborhood using

a ruler, grid paper, and colored pencils.

STEP 1 Fold a sheet of paper in half from

top to bottom and then in half from side to side

STEP 2 Unfold the paper once Cut

along the fold of the top flap to make two flaps

STEP 3 Label the flaps as shown.

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Types of Maps Make the following Foldable to organize information about different types of maps

Monitoring Your Comprehension

As you read this chapter, list details about each type of map Include information about how each map looks, what information it contains, and how it is used

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7.f

ELA6: R 2.4

Learn It! If you know what to expect before reading, it will be easier to understand ideas and

relationships presented in the text Follow these steps to

preview your reading assignments.

1 Look at the title and any illustrations that are included.

2 Read the headings, subheadings, and anything in bold letters.

3 Skim over the passage to see how it is organized Is it divided into

many parts?

4 Look at the graphics—pictures, maps, or diagrams Read their titles,

labels, and captions.

5 Set a purpose for your reading Are you reading to learn something

new? Are you reading to fi nd specifi c information?

Get Ready to to Read

46

Preview

skimmed the chapter, write a short paragraph describing one thing you want to learn from this chapter.

preview this chapter Skim all the main headings and

subheadings With a partner, discuss your answers

Target Your Reading

Use this to focus on the main ideas as you read the chapter.

1 Before you read the chapter, respond to the statements

below on your worksheet or on a numbered sheet of paper

• Write an A if you agree with the statement.

• Write a D if you disagree with the statement.

2 After you read the chapter, look back to this page to see if

you’ve changed your mind about any of the statements

• If any of your answers changed, explain why

• Change any false statements into true statements

• Use your revised statements as a study guide

1 Latitude lines run north to south

2 Degrees, minutes, and seconds can be used to sure distance on maps

3 A map legend is a historic map

4 Longitude lines run north to south

5 A meridian is a longitude line that forms a semicircle

6 Contour lines run up and down on hillsides

7 Contour intervals indicate horizontal distance on topographic maps

8 A map scale is used to measure the weight of heavy maps

9 Geologic maps use color to indicate the different ages of rocks

10 Geologic cross sections can be used to visualize the slope of geologic formations beneath Earth’s surface

Before You Read

ra-d graphs Skim th e caption

LESSON 1

Figure 1 How might pirates have indicated the locations of their buried treasure?

Reading Guide

What You’ll Learn

▼Define latitude and

longitude.

▼Explain how latitude and

longitude are used to

determine a location on

Earth.

▼Demonstrate how map

scales are used.

Why It’s Important

Being able to get from one

pre-Understanding Maps

Maps have been used for many centuries, and there are countless types of maps All show where things are on Earth or where things are in relation to each other For example, a street map shows the locations of streets in relation to other streets, towns, and landmarks Other maps may show the position of a weather system

A single map is like a picture of the location of things at

a given time However, a series of maps drawn over many years can show how Earth’s surface and interior change over time

Because Earth is large, humans need a way to determine where they are located on the planet Imagine telling some-one your exact position on the snow-covered continent of Antarctica It would be difficult to describe Ships’ captains and airplane pilots experience the same problems as they plot their courses across Earth

48 Chapter 1

Science Content

Standards

7.f Read a topographic map and a

geologic map for evidence provided on the

maps and construct and interpret a simple

scale map.

Lesson 1 • Reading Maps 49

A Grid System for Plotting Locations

Mapmakers created a system for identifying locations on

Earth This system uses an imaginary grid of lines that

encir-cles the globe The intersection, or crossing, of these lines can

be used to pinpoint a location

Latitude and Longitude Two sets of lines, called latitude and

longitude, make up this imaginary grid Longitude is the

dis-tance in degrees east or west of the prime meridian The

prime meridian, shown in Figure 2, is a longitude line that

runs from the north pole to the south pole and passes

through Greenwich, England This line represents zero

degrees longitude If you were to travel 180° east or west from

the prime meridian, you would reach another longitude line

called the 180° meridian It lies exactly opposite of the prime

meridian, on the other side of Earth Separately, each of these

lines is a semicircle Together, they form a complete circle

that divides Earth into two imaginary halves—the eastern

and western hemispheres The 180° meridian also forms part

of the International Date Line

Latitude is the distance in degrees north or south of the

equator Earth’s equator, shown in Figure 2, represents zero

degrees latitude It is a latitude line that runs perpendicular

to the longitude lines The equator also divides Earth into

two halves—the northern and southern hemispheres

Lati-tude lines form complete circles The equator forms the

larg-est circle All remaining latitude lines form smaller and

smaller circles as they approach Earth’s poles

Degrees Lines of latitude and longitude are labeled in units

of degrees (°) Because Earth is spherical, each set of the lines

of latitude and longitude make up 360° The north pole is

located at 90° north latitude (90°N) and the south pole is

located at 90° south latitude (90°S) There are an infinite

number of latitude and longitude lines on Earth However, on

a globe, they are generally labeled every 10°

Minutes and Seconds Because Earth is so large, it is

neces-sary to make this location system more precise So, the lines

of latitude and longitude are divided into smaller units Each

degree of latitude or longitude is divided into 60 minutes ( ' )

Each minute is divided into 60 seconds ( " ) The degrees,

minutes, and seconds of a line of latitude or longitude can be

used to pinpoint a precise location on a map

Observe Why do you think

latitude lines are called lels, but longitude lines are called meridians?

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Plotting Locations The lines of latitude and

longitude intersect, or cross each other at an infinite number of places on Earth These intersections describe precise locations on Earth A location on Earth’s surface is described by the intersection of the nearest lines of latitude and longitude The com-bination of the latitude number and the lon-gitude number is referred to as a coordinate Latitude always is listed first when describing

a location For example, Sacramento, nia is located near 38°N latitude by 121°W longitude The coordinates of California’s State Capitol Building in Sacramento, how-ever, is 38°34'33" north (N) latitude by 121°29'29" west (W) longitude Practice find-ing locations by describing the location of the treasure in Figure 3 Then try to determine the latitude and longitude of your hometown

Califor-Which is listed first—latitude or longitude—when describing a location?

Different Views

Most maps are drawn in map view, which

means they are drawn as if you were looking down on an area from above Earth’s surface Map view may also be referred to as plan view Lines of latitude and longitude usually are drawn on a map-view map

Cross sections are drawn in profile view,

which is a drawing showing a vertical section of the ground A profile view is like a side view of a house To help you visualize this concept, a map view and a profile view of

a house are shown in Figure 4 Map views and profile views will be used to describe topographic maps and geologic maps in Les-son 2 Also, you will use profile views when you study models of the inner structures of volcanoes in Chapter 7

How is a profile view related to Earth’s surface?

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Figure 4 The terms map view and plan

view mean the same thing.

Infer Why do you think geographers use the term

map view but architects use the term plan view?

Figure 3 The tiny marks on the x-axis and

y-axis are called tic marks California

occupies land from 32°N to 42°N, and from

114°W to 124°W.

Treasure Map

California Map

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is listed before the actual distance

Lesson 1 • Reading Maps 51

Map Scales and Legends

Maps have two features to help you read and understand

the map They are a map legend and and a map scale

Map Legends

Maps use specific symbols to represent certain features on

Earth’s surface These symbols allow mapmakers to fit neatly

many details on a map All maps include a key, called a map

legend, so you can interpret the symbols A map legend lists

all the symbols used on the map and explains what each

sym-bol means Figure 5 shows an example of a map legend

Map Scales

When mapmakers draw a map, they need to decide how big

or small to make the map They need to decide on the map’s

scale

The map’s scale tells you the relationship between a

dis-tance on the map and the actual disdis-tance on the surface

being mapped The scale can be written as a phrase such as,

“1 centimeter is equal to 1 kilometer.” The scale also can be

written as a ratio, such as 1:100 Because this is a ratio, there

are no units Verbally, you would say, “Every unit on the map

is equal to 100 units on the ground.” If your unit were 1 cm

on the map, it would be equal to 100 cm on the ground If

you drew a map of your school on a scale of 1:1, your map

would be as large as your school

Scale bars also are shown on maps to help determine

dis-tance First, you use a ruler to measure the distance on the

map Then you compare that distance to the scale bar There

are many kinds of scale bars Some examples of scale bars are

shown in Figure 5

S CIENCE U SE V C OMMON U SE

legend

Science Use an explanatory

list of the symbols on a map or

chart You can use the legend to

interpret the different symbols

Common Use a story that is

popularly regarded as cal but not verifiable; a popu-

histori-lar myth Everyone loved the

many legends of the western frontier.

ACADEMIC VOCABULARY

ratio

(noun) the relationship in

quantity or size between two

or more things

The ratio of boys to girls

in Ms Smith’s class was 2:1.

52 Chapter 1 • Mapping Earth’s Surface

The Usefulness of Maps

Maps are used to help you locate places on Earth Latitude and longitude are important for plotting locations on Earth Subdividing latitude and longitude into degrees, minutes, and seconds makes it possible to pinpoint exact locations In Chapter 6, you will use latitude and longitude to plot locations

of earthquakes and faults Map scales are included on maps to represent the actual surface distance that is being represented Map legends often provide a key that explains different

symbols that can be used to interpret maps Depending on your purpose, map views or profile views can be used to help you visualize your surroundings and to find your way around

As populations grow, the development of maps and what they show will help humankind plan for the future

1 Differentiate between

lati-tude and longilati-tude 7.f

2 Define map view in your own

Understanding Main Ideas

3 Explain why coordinates

used to determine locations include degrees, minutes, and

4 Translate the information in

the figure below into words.

5 Diagram a map view and a

profile view of a turkey

6 Which is the correct way to

write location coordinates?

7 Critique the usefulness of a

road map that has no scale

7.f

8 Outline the changes a map

of a city might show as it grew from the first settlers until

Summarize

Create your own lesson

summary as you organize

an outline

1 Scan the lesson Find and

list the first red main

heading.

2 Review the text after

the heading and list 2–3

details about the heading.

3 Find and list each blue

subheading that follows

the red main heading.

4 List 2–3 details, key terms,

and definitions under

each blue subheading.

5 Review additional red

main headings and their

supporting blue

subhead-ings List 2–3 details about

each.

ELA6: R 2.4

Can you map a classroom?

Making a simple scale map of your classroom

is easier than mapping your neighborhood It

also is easy to make exact measurements.

Procedure

1 Make a simple sketch of your classroom.

2 Use a meterstick to measure the:

• length and width of the classroom

• size of the doors and windows

• locations of the desks, tables, shelves, and other objects

3 Mark your measurements on your sketch

Refer to the figure above as an example.

4 Calculate your map scale by dividing the actual distance by the

size of your map area For more help, see Applying Math at the

end of Lesson 2.

5 Use your map scale to calculate the scaled distance for each

measured distance on your sketch Draw all the objects in their

correct locations according to your scale.

6 Draw a map legend Refer to the

figure at the right to get an idea about

what your final drawing might look like.

Analysis

Explain any problems you had when

making your measurements and sketch.

scale calculations Did you make the same mistake over again?

If you repeat certain math errors, think of a strategy to avoid

each type of error.

Science Content Standards

7.f Read a topographic map and a geologic map for evidence provided on the maps and construct

and interpret a simple scale map.

LESSON 2

Figure 6 These surveyors are using equipment

to help them calculate land elevation.

Infer What type of map might they be making?

Topographic and Geologic Maps

Califor-undesirable to build

Topographic Maps

Topography refers to the shape of a surface, including its elevation and the position of its features A special charac-

teristic of topographic maps is that they use lines of equal

elevation to show the shape of Earth’s surface They show natural features, such as mountains, valleys, rivers, lakes, and coastlines They also show cultural features—those created by people —such as buildings, roads, and towns Topographic maps are used for planning, engineering, mil-itary, science, and recreation purposes Figure 6 shows some of the tools that are used to collect the field data that

is used to make these maps

Reading Guide

What You’ll Learn

▼Understand the function

of topographic maps.

▼Explain how topographic

maps show changes in

elevation.

▼Describe geologic maps.

▼Compare topographic

maps and geologic maps.

Why It’s Important

Knowing the shape of Earth’s

surface and the rocks that

make it up helps in the

planning for future uses of

7.c Construct appropriate graphs from

data and develop qualitative statements

about the relationships between variables.

7.f Read a topographic map and a

geologic map for evidence provided on the

maps and construct and interpret a simple

scale map.

7.h Identify changes in natural

phenomena over time without manipulating

the phenomena (e.g., a tree limb, a grove of

trees, a stream, a hillslope).

Also covers: 7.b

Explain If you walked along

a contour line, would you be going uphill, downhill, or nei- ther? Why?

Lesson 2 • Topographic and Geologic Maps 55

Contour Lines

The lines drawn on maps to join points of equal elevation

are called contour lines On topographic maps, contour lines

indicate elevation as the distance above sea level Contour

lines make it possible to measure such things as the height of

a mountain, the depth of the ocean bottom, and the steepness

of a slope The map view in Figure 7 illustrates that each

con-tour line represents equal elevation above sea level

The contour interval is the difference in elevation between

contour lines that are next to each other If the contour

inter-val were 20 feet (6.1 m), then the change in elevation after

five contour lines would be 100 feet (30.5 m) The contour

interval is selected to show the general shape of the terrain

without overcrowding the map with too many lines

Some contour lines are printed with a darker or wider

line than others These are called index contours Generally,

it is only the index contour line that has the elevation

written on it

What is the difference between a contour interval and an index contour?

Topographic Profiles

Sometimes, the map view of an area is not enough You

can get a better feeling for the topography of Earth’s surface

from a profile view, or cross section A profile view looks as

though you were standing on Earth’s surface and looking

toward the horizon Examine the steepness of the slope in

Figure 7 by comparing the map view and profile view

(noun) a space between

objects, units, points, or states

Each of the four runners ran 200-meter intervals in the 800-meter relay race.

Table 1 USGS Topographic Map Symbols

Primary highway Artificial

Secondary

highway

Artificial Unimproved road Artificial

Buildings Artificial

Urban area Artificial

Index contour Landscape

Intermediate

contour

Landscape Perennial streams Landscape

Interactive Table To organize information about topographic

map symbols, visit Tables at ca6.msscience.com

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Symbols on Topographic Maps

Interpreting the colors and symbols on topographic maps is an important step in understanding and using topographic maps For example, contour lines are shown in brown on United States Geologi-cal Survey (USGS) topographic maps Lakes, streams, irrigation ditches, and other water-related features are shown in blue Vegetation is always green Land grids and important roads are red Smaller roads, trails, railroads, boundaries, and other cultural features are shown in black On some USGS topographic maps, the color purple is used to indicate updated informa-tion or changes that were made to an area after the map was originally printed

What does USGS mean?

USGS topographic maps use a wide ety of symbols to display information For example, individual houses may be shown

vari-as small black squares But, for large ings, such as the Rose Bowl in Pasadena, the actual shapes are drawn Only a tint of color, such as pink, is used to show large cities or areas of high population Table 1

build-shows part of the long legend that panies every USGS topographic map

accom-Figure 8 shows a portion of a graphic map that you might use if you were visiting Yosemite National Park See if you can find the name of the river that runs through Yosemite Valley The north direc-tion is at the top of the page on standard USGS topographic maps Also notice that closely spaced contour lines indicate steep slopes Widely spaced lines show areas where the land is relatively flat Contour lines that form a V-shape often indicate the locations of streams or erosion channels

topo-Figure 8 Which direction is

El Capitan from the location of the large red triangle?

56 Chapter 1 • Mapping Earth’s Surface

Lesson 2 • Topographic and Geologic Maps 57

Visualizing Topography

Figure 8

Planning a hike? A topographic map will show you changes in elevation With

such a map, you can see at a glance how steep a mountain trail is, as well as its

location relative to rivers, lakes, and roads nearby.

A V-shaped contour lines can

indi-cate the location of a stream or dry

gulch The bottom of the V points

upstream.

B Where contour lines on a

topo-graphic map are close together,

ele-vation is changing rapidly—and the

trail is very steep!

C Widely spaced contour lines

indi-cate a gentle slope—in some places

the terrain might be almost flat!

Yosemite Valley as it is viewed from the red triangle in the topographic map.

Contributed by National Geographic

A

B

C